1. Field of the Invention
The present invention generally relates to a metal plating process and, in particular, to a novel process and apparatus for plating a workpiece with tin.
2. Prior Art
When insoluble anodes are used in a methane sulfonic acid (MSA) based tin plating process, or other tin electroplating process such as those provided with a tin sulfate or a tin fluoroborate compound, all of the plated tin is derived from the dissolved tin salt. In other words, the tin MSA, tin fluoroborate or tin sulfate is the sole source for the plated tin. The tin compound represents a significant cost to the plating process. Additionally, the acidity of the plating bath builds up over time, necessitating periodic bailouts. After the bailout, tin MSA or the other tin bearing salt and organic additives must be added back into the plating bath. Also, the bailed out solution is a waste product which must be treated. These are all steps in a conventional tin plating procedure which add cost to the final product.
The present invention, as an improvement on the prior art plating process, eliminates, or greatly reduces the need to periodically add a tin salt to the plating bath, and for removing and treating the acid built up in the plating bath.